1992 200TE lack of performance

I have a 1992 200TE estate. It has 107,000 miles and is in great condition. There is one problem and that is that the car sometimes has a severe lack of performance when accellerating. Sometimes when the car is cold it is fine. When it heats up or on hotter days it can sometimes take 4 or 5 seconds for the car to respond properly when you press the accellerator. A new exhaust was fited last year. The fuel injection and carburettor were checked and are ok. The auto gearbox was tested and does not apper to be at fault. There is no air flow meter. I have replaced a broken vacuum value and a cracked breather hose, but nothing has made any difference. I have now been to 4 different mechanics and have not yet found the problem. I really need some suggestions as to what could be causing this. When you press the accellerator sometimes the car seems to draw back and not respond and then suddenly a few seconds later it engages and accellerates. Feels similar to driving a car with a manual choke fully open.

please help.

[Kestas]

Welcome to the Forum.

Two things come to mind - fuel delivery and catalytic converter.

The car could be starved for fuel, usually by an old filter that needs changing.

The ceramic monolith inside the catalytic converter can sometimes break up and restrict exhaust. Give it a kick, if it rattles then you've found your problem. A more involved diagnosis would involve disconnecting the exhaust before the cat and see if the car runs a lot better.

Both these problems would affect acceleration and high speed performance.

Thank you Kestas,

i will try that. In fact my transmission guy mentioned that he had seen a case where the fire retardant material in the exhaust had clogged up the exhaut system, causing a similar problem. I assumed as the exhaust was replaced last year that this was okay. Having said that i only have the car 4 months so it is worth checking.

PS this is a great site.

[mbdoc]

Acceleration performance would be affected both hot & OR cold the same amount if the catalyst was plugged. A quick back pressure test will tell the story on that type of problem.

To accelerate on that engine the computer must change the pressure differential in the fuel distributor. The lower chamber fuel pressure must drop for the engine to increase speed. The upper chamber remains constant. There are several sensor imputs that affect how the computer changes the lower fuel pressure. That would be MY starting point, checking how much the fuel pressures change durning acceleration.

Thanks. This is all very useful. I guess the reason it is more noticeable when hot is because the reves start at about 800rpm when cold but drop off to about 550 when it has warmed up. So there is straightaway a difference in pulling away. But i experienced the problem this morning on my drive in to work which is only 3 miles.

could i have a vacuum leak problem, I had the vacuum value replaced but i think it is for a non catalytic converter model and my car has a cat. Would this make any difference.